Fundamental experiments at liquid helium temperatures

During the past contract year important new results have been obtained in the surface shielding experiment and in the polarized He(3) experiment. In this period the temperature transition in the anomalous surface shielding effect was discovered and investigated. A complete report/thesis was written covering all the shielding effect work to date. In the polarized He(3) experiment measurements were made of the longitudinal nuclear relaxation times of dilute mixtures of polarized He(3) in liquid He(4) molar concentrations of 7 x 10(-3) at 4.2 K in magnetic fields between 36 x10(-6)G and 2 mG in order to search for techniques which would allow the achievement of very long relaxation times. By using a solid H(2) wall coating in a 1-cm diameter cell, a relaxation time in excess of five days was obtained. Fabrication of all internal components of the prototype electron/positron thermalizer was completed during the past contract year. The central apparatus was assembled and wired. A laboratory was equipped, necessary cyrogenic and vacuum equipment was constructed, and preparations were made for low temperature runs of the thermalizer prototype during the 1976-77 contract year.